Research On Mechanical Performance Of Vehicle-Large Displacement Expansion Joint Coupled System

With the rapid development of our country,the cross-regional turnover of people and logistics transportation requirements posed new challenges to the road traffic in China.Various long-span bridges have been built,the higer requirements are put forward for expansion joints which play the role of adjusting deformation.Ensuring the reliablity of large displacement expansion joints and improving the safety and comfort of passing vehicles have become new challenges facing the development of bridges in China.Due to the large-scale use time of large displacement expansion joints is short,the industry standard for the design and maintenance of large displacement expansion joint in China is not mature,and national standards have not been formulated.The existing relevant provisions only give a simple static performance description.The existing research on the large displacement expansion joint is still in the initial stage and is not systematic and in-depth.Therefore,the influence of vehicle parameters and expansion joint parameters on the mechanical performance of the vehicle-large displacement expansion joint coupled system(vehicle-joint coupled system)is analyzed by simulation in this dissertation.and The interaction between the vehicle and the expansion joint from the perspective of dynamics is studied,aiming to provide certain theoretical basis for the design,maintenance and monitoring management of expansion joint.The main contents of this dissertation are as follows:(1)According to the working principle and stress characteristics of vehicle tire,a tire equivalent model which is Beam188 + Solid95 mixed structure to simulate the complex rubber/cord structure of belt and caecass is proposed.And based on the mechanical principle of composite material,the stiffness equivalent method,a calculation method of equivalent material parameters of belt layer,is proposed.Compared with the test results,the validity of the stiffness equivalent method applied to the tire equivalent model is verified,which lays a foundation for the establishment of the finite element(FE)model of the vehicle-joint coupled system.(2)Tests are carried out on the elastic parts of large displacement expansion joint,and the stiffness characteristics of the elastic parts are determined.On this basis,the rigid-flexible hybrid model of the 1/4 vehicle-joint coupled system was established using Recur Dyn software.This model can accurately simulate the dynamic process of vehicle passing through the expansion joint.The simulation experiments are carried out with this model to study the characteristics of the vibration response of the coupled system in detail.And the influence of vehicle speed on the vibration response of the coupled system and the influence range of the wheel on the vibration of the center beam are discussed.(3)Considering the discontinuity of the center beams and the rigid displacement of the tire belt,the dynamic models of vehicle-joint coupled system are established using different vehicles.The new integration method is used to solve these models,and the corresponding calculation program is compiled.The comparison of the simulation results of the coupled dynamic model and the uncoupled dynamic model with the simulation results of the rigid-flexible hybrid model respectively verifies the necessity and validity of the coupled dynamic model.(4)Using the dynamic model of the heavy vehicle-expansion joint coupled system,the influence of heavy vehicle parameters and expansion joint parameters on the impact coefficient of the expansion joint center beam and the dynamic load coefficient of the vehicle tire is studied in detail.The research results show that impact coefficient of No.1 center beam is the largest,and the vibration impact coefficient of the center beam and the dynamic load coefficient of the vehicle tire are significantly affected by the position of the wheel relative to the beam,vehicle type,speed,gap width and the stiffness of the elastic part of the center beam.On this basis,the design suggestions of elastic elements are given.The impact coefficient of the center beam and the tire dynamic load coefficient of the heavy vehicle will exceed the recommended values of the existing standards,which provides a theoretical basis for the improvement and formulation of the releted standards.(5)According to the vibration characteristics of the car passing through the expansion joint,selecting the maximum acceleration value as the comfort evaluation index.using the dynamic model of the car-large displacement expansion joint coupled system,the effects of vehicle parameters and expansion joint parameters on car comfort are studied in detail.The results show that when the car drives through the expansion joint,the vertical direction of the seat surface is affected by the filter effect of the seat elastic part as 1Hz low-frequency vibration,and the lateral and longitudinal performance is the superposition of the low-frequency vibration and the high frequency vibration.The car comfort is significantly affected by the position of the wheel relative to the crossbeam,the speed of the car,the distance of a parallel driving lorry,the gap width of the expansion joint and the stiffness of the elastic part of the center beam,but it is less affected by the stiffness of the elastic element of the crossbeam.The dynamic load coefficient of car tire is only affected by the speed,the distance of a parallel driving lorry,and the gap width of the expansion joint.The research results provide a reference for vehicle driving and bridge management(6)The vibration test results of the vehicle driving through the large displacement expansion joint show that the vibration decay time of the center beam caused by the vehicle is less than 0.1s,and the maximum vibration speed increases with the increase of the vehicle speed.The simulation results of the vehicle-expansion coupled system dynamic model are in good agreement with the test results,which provide the experimental basis for the application of dynamic model and large displacement expansion joint products.